Directional flow control valves of numerous variety are available that provide many types of control characteristics which are often tailored to specific applications. Although sharing the common function of directional flow control, these valves vary considerably in construction and operation.
A common simple type of directional flow control valve is a two-position, three-way valve. A facility for providing two finite positions of a moving element yields fluid flow control by opening and closing flow paths through the valve by placement of the moving element in definite positions.
A conventional method of valve actuation to position the moving element is through use of a solenoid. With a solenoid actuator, electric energy is applied to a coil, which creates a magnetic field that draws an armature into the coil. The armature motion is typically transmitted through a rod, which in turn positions the moving member.
Conventional three-way fluid flow control valves as thus far described are generally simple in construction and provide limited directional control through the valve between a first port and either of a second or a third port. When more complicated control mechanisms are required to be provided by the valve in order to adequately control a complicated fluid control scheme of a system, such a conventional valve must be supplemented with additional componentry. When functions other than solely providing directional control are required, additional fluid flow control mechanisms such as check valves and additional directional control valves are added to the system. When available space does not permit the addition of ancillary flow control mechanisms or functional response of amassed individual components is unacceptable, the conventionally available fluid flow control components are inadequate. Therefore, with complicated fluid control schemes a new flow control mechanism is required.